The present invention relates generally to aircraft ground power systems and, more particularly, to an aircraft ground power apparatus designed to respond “on-demand” based on aircraft charging demands. The aircraft ground power apparatus includes an energy storage device capable of providing immediate and sufficient power in conjunction with an internal combustion engine that can be automatically started to compliment the energy storage device and charge the energy storage device to provide sufficient aircraft ground power while saving fuel.
Aircraft sitting at a gate or terminal will normally cease engine operation along with any internal or auxiliary power generating equipment. Particularly, should the aircraft intend to remain on the ground, such as at a terminal, for any significant length of time, the aircraft systems are typically powered from auxiliary systems designed to allow the aircraft systems to operate auxiliary equipment without the need to operate the aircraft engines. The needed auxiliary power is often supplied by portable ground power units carried on wheeled trailers.
When an aircraft is at rest and in need of power, a ground power unit is towed into position by a tractor or tug. Once in place, the aircraft ground power unit is uncoupled from the tractor and its electrical cable is connected to the aircraft by plugging the cable into a receptacle provided on the aircraft. A combination engine driven generator incorporated within the ground power unit is operated to generate power that is supplied to the aircraft via the electrical cable. Typically, the aircraft ground power is connected to the aircraft, the unit is started, and then the operator leaves the unit unattended until power is no longer needed from the aircraft ground power unit. In the interim, the engine and generator operate at an operational or high speed to deliver power to the aircraft independent of actual load. That is, aircraft ground power unit typically requires that the engine and generator be running at full speed to provide correct frequency and power and/or supply a full load to the aircraft. Therefore, while in operation, the aircraft ground power unit is set to deliver a maximum amount of power to the aircraft and, thereby, runs at full speed.
However, while the aircraft ground power unit is connected to an aircraft, the power consumption needs of the aircraft are not necessarily constant or consistent. That is, the individual power consumption needs may vary widely and may even be intermittent. For example, when the aircraft has passengers on board the aircraft may require a relatively large amount of power from the aircraft ground power unit to provide sufficient cooling by the aircraft air conditioning systems. On the other hand, when the aircraft is empty, the aircraft may require a relatively low amount of power from the aircraft ground power unit, such as when only a pilot is on board and only preflight navigational systems are in operation.
Regardless of the power consumption needs of the aircraft, the known engine and generator units operate at full operational speed for the duration of the connection unless an operator arrives to shut down the unit. Accordingly, although the full power generation capabilities of the aircraft ground power unit is not necessary, the engine and generator are continuously run. Accordingly, excess fuel is consumed and additional noise and exhaust are created unnecessarily.
Additionally, aircraft ground power units are often switched from departing aircraft to newly arrived aircraft. When disengaging an aircraft ground power unit from a departing aircraft, the generator of the aircraft ground power unit is powered down and the aircraft ground power unit is removed from the departing aircraft and transported to the newly arrived aircraft. Once at the newly arrived aircraft, the aircraft ground power device is attached to the newly arrived aircraft and then the engine and generator of the aircraft ground power unit must be restarted. However, before power is delivered to the newly arrived aircraft, the generator of the aircraft ground power unit must again reach full operational speed. Specifically, an operator must first start the generator and wait until the generator is at operational speed before power is delivered to the aircraft. This delay in reaching operational power can create unnecessary power consumption from the aircraft's auxiliary power systems while the aircraft awaits power from the aircraft ground power unit. That is, although the aircraft has come to rest and is connected to a aircraft ground power unit, the aircraft continues to draw operational power from internal auxiliary power systems to drive systems such as passenger ventilation and air conditions systems until the generator of the aircraft ground power unit reaches full operational speed and power is finally delivered to the aircraft. This delay in power delivery from the aircraft ground power unit to the aircraft, albeit relatively short, can result in prolonged power draws from the aircraft's internal auxiliary power system which must later be recharged.
It would therefore be desirable to design an aircraft ground power unit that operates on-demand and is dynamically adjustable to the power consumption needs of an associated aircraft. Specifically, it would be desirable to have an on-demand aircraft ground power device that matches the power requirements of the associated aircraft that does not necessarily run the engine continuously.